ISSN: 2278 – 7798
International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 5, Issue 8, August 2016
A Voltage-Controlled Switched Boost Inverter-Based
PMBLDCM Drive for Air Conditioners
K Sabarinath *, P RamaKrishna**
*
**
Department of EEE, Amrita Sai Institute of Science & Technology, Paritala, Krishna Dt, A.P, India
Department of EEE, Amrita Sai Institute of Science & Technology, Paritala, Krishna Dt, A.P, India
Abstract- This paper deals with a switched boost inverter as a
single-stage power-factor-correction converter for a permanent
magnet (PM) brushless dc motor (PMBLDCM) fed through a
diode bridge rectifier from a single-phase ac mains. A threephase voltage-source inverter is used as an electronic
commutator to operate the PMBLDCM driving an airconditioner compressor. The speed of the compressor is
controlled to achieve optimum air-conditioning using a concept
of the voltage control at dc link proportional to the desired speed
of the PMBLDCM. The stator currents of the PMBLDCM during
step change in the reference speed are controlled within the
specified limits by an addition of a rate limiter in the reference dc
link voltage. The proposed PMBLDCM drive (PMBLDCMD) is
designed and modelled, and its performance is evaluated in
Matlab–Simulink environment. Simulated results are presented
to demonstrate an improved power quality at ac mains of the
PMBLDCMD system in a wide range of speed and input ac
voltage. Test results of a developed controller are also presented
to validate the design and model of the drive.
Index Terms- DC-link voltage balance, PMBLDCM, power
quality (PQ), Air conditioner (AC).
I. INTRODUCTION
Air-conditioners (Air-Cons) constitute a considerable amount of
load in AC distribution system. However, most of the existing
air-conditioners are not energy efficient and thereby, provide a
scope for energy conservation. Air-Cons in domestic sector are
usually driven by a single-phase induction motor; the
temperature in the air conditioned zone is regulated over a
hysteresis band through the „on/off‟ control of the compressor
motor. Therefore, the motor is operated only at full load
(compressor „on‟) at nearly constant speed, i.e., rated speed, [1]
because these motors achieve maximum efficiency near the rated
load only. The „on/off‟ control provides inefficient temperature
control with increased losses in the motor during frequent
„on/off‟ operation. Efforts to improve the efficiency of the
existing air-con system using new mechanical and electronic
system designs have resulted in marginal improvement in system
efficiency; however, the variable speed operation of the air
conditioner significantly improves system efficiency [2].
Moreover, the compressor driven by a motor with speed control
delivers the desired cooling capacity and maintains the room
temperature effectively and efficiently. Permanent magnet
brushless DC motor (PMBLDCM) drives are being employed in
many variable speed applications due to their high efficiency,
silent operation, compact size, high reliability, ease of control,
and low maintenance requirements. It is a good option for an air
conditioner compressor. PMBLDCM is operated through a threephase voltage source inverter (VSI), which is fed from single
phase AC supply using a diode bridge rectifier (DBR), followed
by a smoothening DC link capacitor. PMBLDCM is supplied by
three-phase rectangular current blocks of 120° duration, in phase
with the constant part of the back EMF waveform. These motors
need rotor-position information only at the commutation points,
e.g., every 60°electrical in the three-phase, requiring a simple
controller for commutation [3-7].The PMBLDC motor is
operated at a constant torque(i.e., rated torque) with speed
control to improve energy efficiency [8]. In fact, the back-EMF
of the PMBLDCM is proportional to the motor speed and the
developed torque is proportional to its phase current [3-6];
therefore, a constant torque is maintained by a constant current in
the stator winding of the PMBLDCM, whereas the speed can be
controlled by varying the terminal voltage of the motor. A new
speed control scheme that uses DC link voltage proportional to
the desired speed of the PMBLDC motor is used in this work.
VSI control is based on the rotor position signals and used only
for electronic commutation of the PMBLDC motor.
The most commonly used topology for PMBLDCM Drive fed
from single-phase AC mains uses a diode bridge rectifier (DBR)
followed by a smoothening DC capacitor. It draws a pulsed
current with a peak higher than the amplitude of the fundamental
input current at ac mains due to an uncontrolled charging of the
dc link capacitor. This results in poor power quality (PQ) at ac
mains in terms of poor power factor (PF) of the order of 0.728,
high total harmonic distortion (THD) of ac mains current at the
value of 81.54%, and high crest factor (CF) of the order of 2.28
with 67% efficiency of the drive. Therefore, many Power Quality
(PQ) problems arise at input AC mains including poor power
factor, increased Total Harmonic Distortion (THD) and high
Crest Factor (CF) of AC mains current etc. These PQ problems
as addressed in IEC 61000-3-2especially in low power
appliances become severe for the utility when many such drives
are employed simultaneously at nearby locations[9].Therefore,
PMBLDCM drives having inherent Power Factor Correction
(PFC) become the preferred choice for the Air-Cons. The PFC
converter draws sinusoidal current from AC mains in phase with
its voltage.
II. PFC SWITCHED BOOST INVERTER FED
PMBLDCMD
Fig. 1 shows voltage controlled PFC switched boost inverter fed
permanent magnet brushless dc motor. The single phase AC
mains supply is rectified into dc by the single phase bridge
rectifier and rectified dc is controlled by switched boost inverter.
2697
All Rights Reserved © 2016 IJSETR
ISSN: 2278 – 7798
International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 5, Issue 8, August 2016
Fig 1. Schematic diagram of PFC Switched boost inverter fed
PMBLDC Motor
(a)
A. Design of PFC Switched Boost Inverter
Switched boost converter (SBC) is able to buck or boost the
input voltage in a single stage to get the desired output voltage.
Fig.1 shows the schematic of a three phase SBI in which a
switched boost network comprising of one active switch (S), two
diodes (Da, Db), one inductor (L) and a capacitor (C) is
connected between voltage source Vg and inverter bridge.
Similar to ZSI, the SBI utilizes the shoot-through state of the Hbridge inverter (both switches in one leg of the inverter are
turned on simultaneously) to boost the input voltage Vg to Vc.
To explain the steady-state operation of the SBI, assume that the
inverter is in shoot-through zero state for duration D.TS in a
switching cycle TS. The switch S is also turned on during this
interval. As shown in the equivalent circuit of Fig. 4(a), the
inverter bridge is represented by a short circuit during this
interval. The diodes Da and Db are reverse biased (as VC >Vg),
and the capacitor C charges the inductor L through switch S and
the inverter bridge. The inductor current in this interval equals
the capacitor discharging current. For the remaining duration in
the switching cycle (1 − D).TS, the inverter is in non-shoot
through state, and the switch S is turned off. The inverter bridge
is represented by a current source in this interval as shown in the
equivalent circuit of Fig.4 (b).
(b)
Fig.3. (a) Equivalent circuit diagram of SBI during the
interval DTs (b) Equivalent circuit diagram of SBI during
the interval (1 - D)Ts.
Under steady-state, the average voltage across the inductor and
the average current through the capacitor in one switching cycle
should be zero.
Using volt–second balance, we have
The average dc link voltage Vi can be calculated as
The peak output AC line voltage is given by,
=
It is observed from equation (3) and (5) that VC can be boosted
and Vom can be bucked or boosted based on the shoot-through
duty ratio D and modulation index M.
B. Control Strategy for SBI fed PMBLDC Motor
Fig 2. Circuit diagram of a three-phase Switched Boost
Inverter.
Now, the voltage source Vg and inductor L together will supply
power to the inverter and the capacitor through diodes Da and
Db. The inductor current in this interval equals the capacitor
charging current added to the inverter input current. Note that the
inductor current is assumed to be sufficient enough for the
continuous conduction of diodes Da and Db for the entire
interval (1 − D)TS.
The BLDC motor provides an attractive candidate for sensor less
operation because the nature of its excitation inherently offers a
low-cost way to extract rotor position information from motor
terminal voltages. A Permanent Magnet brushless drive that does
not require position sensors but only electrical measurements is
called a sensor less drive [15]. For three-phase BLDC motor at
one time instant, only two out of three phases are conducting
current and the no conducting phase carries the back-EMF. If the
zero crossing of the phase back EMF can be measured, we can
know when to commutate the current. Sensing methods for the
PMBLDC motors and generators are classified in two categories;
direct and indirect back-EMF detection [15]. Direct back-EMF
detection methods: the back- EMF of floating phase is sensed
and its zero crossing is detected by comparing it with neutral
point voltage. The methods can be classified as:
Direct back-EMF detection methods are
2698
All Rights Reserved © 2016 IJSETR
ISSN: 2278 – 7798
International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 5, Issue 8, August 2016

Back-EMF Zero Crossing Detection (ZCD) or Terminal
Voltage Sensing and PWM strategies. [14]
Indirect back-EMF detection methods:
 Back-EMF Integration, Third Harmonic Voltage
Integration and Free-wheeling Diode Conduction or
Terminal Current Sensing [15].
Here position of the BLDC motor is obtained by employing zero
crossing back emf detection method and thus eliminating
position sensor requirement [8].
The PMBLDCMD consists of an electronic
commutator, a SBI, and a PMBLDCM.
B. The PMBLDC Motor Drive
The PMBLDCM drive has an electronic commutator, a voltage
source inverter and a PMBLDC motor as the main components.
1) Electronic Commutator:
The Electronic commutator uses signals from Hall-effect position
sensors to generate the switching sequence for the VSI.
2) Voltage Source Inverter:
Fig.4 shows the PMBLDC Motor Drive system.
C. Mathematical Modelling of PMBLDC Motor Drive
The modelling of PMBLDCM drive involves modelling of the
PFC converter and PMBLDCM drive. These components are
modelled in the form of mathematical equations and the
complete drive is represented as a combination of these models.
A. PFC Converter
The PFC converter consists of a DBR at front end and a buck or
boost mechanism with Voltage source inverter. The PFC
converter modelling consists of the modelling of a speed
controller, a reference current generator, and a PWM controller
as given below.
1) Speed Controller: The Speed Controller is a PI controller
which closely monitors the speed error as an equivalent voltage
error and generates control signal (Ic) to minimize the error. If at
kth instant of time, V*dc(k) is reference DC link voltage, Vdc(k)
is sensed dc link voltage then the voltage error Ve(k) is
calculated as,
The output of the controller Ic(k) at kth instant is given as,
Where, Kpv and Kiv are the proportional and integral gains of the
voltage PI controller.
2) Reference Current Generator: The reference current at the
input of the Cuk converter is,
Fig.4 Brushless dc motor drive system
The output of VSI to be fed to phase „A‟ of the PMBLDC motor
is given as,
Where Vao, and Vno are voltages of phase A and neutral
terminal with respect to virtual mid-point of the dc link. Using
similar logic Vbo, Vco, Vbn, Vcn are generated for other two
phases of the VSI feeding PMBLDC motor. The voltages Van,
Vbn, and Vcn are voltages of three-phases with respect to the
motor neutral terminal (n).
3) PMBLDC Motor:
The PMBLDCM is represented in the form of a set of differential
equations given as,
where ud is the unit template of the ac mains voltage, calculated
as,
3) PWM Controller:
The reference input current of the Cuk converter (i*d) is
compared with its current (id) sensed after DBR to generate the
current error Δi. This current error is amplified by gain kd and
compared with fixed frequency (fs) sawtooth carrier waveform
md(t) to get the switching signal for the MOSFET of the Cuk
converter as,
In these equations, ia, ib, and ic are currents, and ea, eb, and ec
are the back EMFs of PMBLDCM, in respective phases; R is the
resistance of motor windings/phase and L is the inductance. The
developed torque Te in the PMBLDCM is given as,
The mechanical torque equation of motion is given by,
where S denotes the switching of the MOSFET of the Cuk
converter representing „ON‟ position with S=1 and its „OFF‟
position with S=0.
Where ωr is the derivative of rotor position θ, P is the number of
poles, Tl is the load torque in Newton meters, J is the moment of
inertia in kilogram square meters, and B is the friction coefficient
2699
All Rights Reserved © 2016 IJSETR
ISSN: 2278 – 7798
International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 5, Issue 8, August 2016
in Newton meter seconds per radian. The derivative of rotor
position is given as,
These equations represent the dynamic model of the PMBLDC
motor.
III. SIMULATION RESULTS
The proposed PFC Switched boost inverter fed PMBLDC
motor performance is studied in MATLAB/SIMULINK
platform. The fig 5(a), (b) shows the simulated circuit of voltage
controlled PFC Switched boost inverter fed PMBLDC drive
system, control circuit for PFC converter. The switched boost
inverter output line to line voltage and current, stator current and
back EMF of motor, speed and torque of motor are presented .it
is observed that the inverter output and currents are having the
THD of 1.92%.the speed of the PMBLDC controlled by
controlling dc bus voltage. The time delay of 0.1sec is allowed in
the simulation to study the starting characteristics of the
PMBLDC Motor.
Fig 5(b)
Table: 1 Hall Signals
Fig 6 DC link Voltage
A. Simulation circuit of Proposed PFC PMBLDCM Drive
Fig 7 SBI output Voltages and currents
Fig 5(a)
B. Simulation Circuit of Control mechanism
Fig 8 PMBLDC Motor Stator current and back emf
2700
All Rights Reserved © 2016 IJSETR
ISSN: 2278 – 7798
International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 5, Issue 8, August 2016
[6] T. J. Sokira and W. Jaffe, Brushless DC Motors: Electronic Commutation and
Control. New York: Tab, 1989.
[7] J. R. Hendershort and T. J. E. Miller, Design of Brushless PermanentMagnet
Motors. Oxford, U.K.: Clarendon, 1994.
[8] J. F. Gieras and M. Wing, Permanent Magnet Motor Technology—Design
and Application. New York: Marcel Dekker, 2002.
[9] B. Singh, B. N. Singh, A. Chandra, K. Al Haddad, A. Pandey, and D. P.
Kothari, “A review of single-phase improved power quality ac–dc converters,”
IEEE Trans. Ind. Electron., vol. 50, no. 5, pp. 962–981, Oct. 2003.
[10] N. Mohan, M. Undeland, and W. P. Robbins, Power Electronics:
Converters, Applications and Design. Hoboken, NJ: Wiley, 1995.
[11] Limits for Harmonic Current Emissions (Equipment Input Current ≤ 16 A
Per Phase), Int. Std. IEC 61000-3-2, 2000.
[12] S. Cuk and R. D. Middlebrook, “Advances in switched-mode power
conversion Part-I,” IEEE Trans. Ind. Electron., vol. IE-30, no. 1, pp. 10–19, Feb.
1983.
[13] C. J. Tseng and C. L. Chen, “A novel ZVT PWM Cuk power factor
corrector,” IEEE Trans. Ind. Electron., vol. 46, no. 4, pp. 780–787, Aug. 1999.
[14] B. Singh and G. D. Chaturvedi, “Analysis, design and development of single
switch Cuk ac–dc converter for low power battery charging application,” in Proc.
IEEE PEDES, 2006, pp. 1–6.
[15] C. L. Puttaswamy, B. Singh, and B. P. Singh, “Investigations on dynamic
behavior of permanent magnet brushless dc motor drive,” Elect. Power Compon.
Syst., vol. 23, no. 6, pp. 689–701, Nov. 1995.
[16] A. Ravindranath, S. Mishra, and A. Joshi, “Analysis and PWM Control of
Switched Boost Inverter,” Accepted for publication in IEEE Trans. Ind.
Electron., 2013.
[17] F. Z. Peng, “Z-source inverter,” IEEE Trans. Ind. Appl., vol. 39, no. 2, pp.
504–510, Mar./Apr. 2003.
[18] Y. Zhou, and W. Huang, “Single-stage boost inverter with coupled
inductor,” IEEE Trans. Power Electron., vol. 27, no. 4, pp. 1066– 1070, Apr.
2012.
[19] S. Mishra, A. Ravindranath, and A. Joshi, “Inverse Watkins-Johnson
topology based inverter,” IEEE Trans. Power Electron., vol. 27, no. 3, pp. 1066–
1070, Mar. 2012.
.
Fig 9. PMBLDC Motor Speed
Fig 10. PMBLDC Motor Torque
IV. CONCLUSION
The permant magnet brush less DC Motor is suitable drive for
compressor of air-conditioner. Since the characteristics of
PMBLDC motor with power factor corrected switched boost
inverter are better than the characteristics of the single phase
motors used for air conditioners. These motors suffer from the
power factor and harmonic currents but the proposed voltage
controlled power factor corrected switched boost inverter fed
PMBLDC motor has less harmonic distortion and high power
factor.
AUTHORS
First Author – K.Sabarinath, he received his B.Tech degree in
Electrical and Electronics Engineering from
Gandhiji Institute of Science and Technology in
2013. He is currently pursuing M.Tech Power
Electronics in Amrita Sai Institute of Science
and Technology, Paritala, A.P, India. His
interested research areas are Power Electronic
Applications to ASDs.
REFERENCES
Second Author – P Rama Krishna, he received his B.Tech
degree in Electrical and Electronics Engineering
from Nalanda Institute of Engineering and
Technology, Sattenapalli (A.P), India, in 2012.
M.Tech degree in Power Electronics from Mother
Theresa Institute of Science and Technology,
Sattupalli (Telangana), India, in 2014. He is
currently working as a Assistant Professor in
Amrita Sai Institute of Science and Technology, Paritala, A.P,
India. His interested research areas are Power Electronics &
Drives
and
Power
System.
[1] Ravindranath Adda, Avinash Joshi, and Santanu Mishra, “Pulse Width
Modulation of Three-Phase Switched Boost Inverter” 978-1-4799-03368/13/$31.00 ©2013 IEEE.
[2] S. Mishra, A. Ravindranath, and A. Joshi, “Switched-boost Inverter based on
Inverse Watkins-Johnson Topology,” in Proc. 3rd IEEE Energy Conversion
Congress and Exposition (ECCE), Phoenix, 2011, pp. 4208–4211.
[3] Sanjeev Singh and Bhim Singh, “A Voltage-Controlled PFC Cuk ConverterBased PMBLDCM Drive for Air-Conditioners” IEEE Transactions on Industrial
Applications, Vol: 48 No:2, March/April 2012.
[4] A. Ravindranath, S. Mishra, and A. Joshi, “A PWM control strategy for
switched boost inverter,” in Proc. 3rd IEEE Energy Conversion Congress and
Exposition (ECCE), Phoenix, 2011, pp. 4208–4211.
[5] T. Kenjo and S. Nagamori, Permanent Magnet Brushless DC Motors. Oxford,
U.K.: Clarendon, 1985.
2701
All Rights Reserved © 2016 IJSETR